autoplant isogen item code

Hi, I am running AutoPLANT V8i SS4 on AutoCAD 2012. We have ceated commodity codes for components and are using these on the Isometric BOM using the ITEM-CODE.

Our Bolts have different sizes but all have the same Commodutycode/Item Code. If I run an isometric with two different size bolts with the same Commoditycode/Item I am getting an _1 at the end of the of the Bolts Commoditycode/Item code. If there aremore sizes it will add _ 2, _ 3 etc. See example below. How can I stop the _1, _2 etc from appearing on the Commoditycode/Item code